An example of a system as specified in the preamble is a wireless radio-frequency (RF) communication receiver. Such a receiver has to process signals with an extremely wide dynamic range. The dynamic range is the range of signal levels that can be processed without running into problems involving noise and signal distortion caused by clipping. The processing invariably entails high levels of amplification in the signal path. This poses major technical challenges towards the fully integrated implementation of RF receivers. Typically, offset levels, induced by device mismatch, can exceed by far received signal amplitudes.
Receiver stages are typically DC-coupled if the receiver is integrated in monolithic form. Problems associated with uncontrolled DC-offset include the requirement that the dynamic range of the ADC be significantly higher than that of an ADC with no offset compensation at all. Also, the offset could result in grossly distorted signals and high bit-error rates. This necessitates some form of DC-offset compensation in the receive path.
The most common technique used to compensate for offset effects is the trimming of the offset in the manufacturing environment. This has several drawbacks. First, the process of trimming tends to be expensive. Second, the stress imposed on the chip after packaging tends to shift the offset levels. This, often, forces the manufacturer to have the offset trimmed after packaging. Further complications arise from the fact that most critical tests have to be performed after DC-offset removal.